A conventional domestic fan typically includes a set of blades or vanes mounted for rotation about an axis, and drive apparatus for rotating the set of blades to generate an air flow. The movement and circulation of the air flow creates a ‘wind chill’ or breeze and, as a result, the user experiences a cooling effect as heat is dissipated through convection and evaporation.
Some fans, such as that described in U.S. Pat. No. 5,609,473, provide a user with an option to adjust the direction in which air is emitted from the fan. In U.S. Pat. No. 5,609,473, the fan comprises a base and a pair of yokes each upstanding from a respective end of the base. The outer body of the fan houses a motor and a set of rotating blades. The outer body is secured to the yokes so as to be pivotable relative to the base. The fan body may be swung relative to the base from a generally vertical, untilted position to an inclined, tilted position. In this way the direction of the air flow emitted from the fan can be altered.
WO 2010/100451 describes a fan assembly which does not use caged blades to project air from the fan assembly. Instead, the fan assembly comprises a cylindrical stand which houses a motor-driven impeller for drawing a primary air flow into the stand, and an annular nozzle connected to the stand and comprising an annular air outlet through which the primary air flow is emitted from the fan. The nozzle defines a central opening through which air in the local environment of the fan assembly is drawn by the primary air flow emitted from the air outlet, amplifying the primary air flow.
The stand comprises a base and a body mounted on the base. The body houses the motor-driven impeller. The body is secured to the base so that that body can be moved relative to the base from an untilted position to a tilted position by pushing or sliding the body relative to the base. The base has a concave upper surface upon which are mounted a plurality of L-shaped rails for retaining the body on the base, and for guiding the sliding movement of the body relative to the base as it is moved to or from a tilted position. The body has a convex lower surface upon which a convex tilt plate is mounted. The tilt plate comprises a plurality of L-shaped runners which interlock with the rails on the base as the tilt plate is secured to the base so that flanges of the runners are located beneath conformingly shaped flanges of the rails.
The base further comprises a plurality of support members for supporting the body on the base. Each support member comprises a ball bearing and a spring which urges the ball bearing away from the support. The tilt plate comprises curved races for receiving the bearings and within which the bearings move as the body is tilted relative to the base. The spring force of the springs urges the body away from the base, against the weight of the body, nozzle and internal components of the body, which in turn urges together facing surfaces of the flanges of the rails and the runners so that the body is maintained in a desired tilted position by virtue of friction between the rails and the runners.
A problem associated with this mechanism for maintaining the body in a tilted position relative to the base is that, depending on the material from which the springs are formed, relaxation of the springs over time can cause the body to move gradually closer to the base, reducing the friction forces between the rails and the runners. If this relaxation is severe, this can compromise the ability of the mechanism to maintain the body in a tilted position.